What is the collective noun for historians? A symposium, a colloquy, a dispute? However one styles them, there are a lot of historians about at Hay, and it seems an unmissable opportunity to pose two questions. Is this decade as tumultuous as it seems - with the multiple disorders of the war on terror, economic collapse, climate change and now, in the UK at least, a political firestorm? And do historians have anything valid to say about this decade, the noughties, or is it too early to begin to make judgments?

Andrew Roberts, media combatant and historian, is in no doubt that we live in interesting, perhaps even cataclysmic, times. "This is a massively tumultuous decade," he tells me. "Obviously, 9/11 is going to be seen as the end of one chapter and the beginning of the next in every history book that our children are going to read. And then we have the economic collapse and the sheer sense of fin de siécle that we've got right now."

But he doesn't factor into this sense of apocalypse the paranoia and paralysis that is currently gripping Westminster. "I don't think the expenses scandal is going to turn into anything constitutional; it's just going to be a straightforward election issue, and it might not be as huge an election issue by next May as we think it's going to be right now." Terrorism, radical Islam and nuclear proliferation - especially a nuclear Iran - are the geopolitical keys for Roberts; and he reckons the credit crunch might yet turn into a generation-defining Great Depression.

This big-bang historical theorising is not shared by Richard Overy, professor of history at Exeter University and author of The Morbid Age: Britain Between the Wars. In the brilliant lecture he gave at the weekend, he talked of the sense of civilisation in decay that swept Britain in that period, as a coda to which he points to parallels with our own times and issues a warning not to fall into the same catastrophist trap.

Overy is a very persuasive gradualist. "I say calm down," he tells me. "There are very long-term changes that occur through time that are not going to be much affected by what's happened this year, that year or the year after. If you look at the whole of human history, not just the last 10 years, human beings are incredibly adaptive and flexible. They cope with whatever is thrown at them. Our image at the moment is that we are negative, state-led people bound to our computers who are going to go down in some huge fireball. It just isn't the case."

He argues that governments have used the war on terror for their own ends, deliberately fuelling anxieties to get repressive policies passed. That will play well with the political left. But they may find his views on climate change less attractive: in essence he thinks the jury is still out on the degree to which global warming is man-made. "There have been a great many times when the climate has got much colder and much warmer," he says. "You could grow grapes and apricots in East Anglia in the 15th century, and that's nothing to do with industry and cars."

Richard Evans, regius professor of modern history at Cambridge, who gave a lecture drawing on the third and final volume of his history of the Third Reich, is largely in agreement with Overy. When I ask him whether 9/11 could be seen as a watershed, he parries: "All I would say is what Zhou Enlai said when he was asked about the consequences of the French revolution - it's too early to tell." Historians distrust immediate judgments: Evans, a purist, thinks the interpretative fog might start to lift after about 30 or 40 years.

"What interests journalists and the reading public is often very different from what interests historians," he says. "Journalists are interested in the moment, whereas historians write about longer trends." Overy makes a similar point. "The headlines," he says, "will mask some of the underlying continuities, or the things that were not in fact damaging or dangerous but nonetheless contribute a great deal to moulding the future." And it's not just journalists who deal in headlines, he adds. Some historians are attracted by them, too, overplaying the "moments of drama".

Niall Ferguson, whose most recent book is The Ascent of Money, thinks all decades are tumultuous. "Name one that wasn't." I offer the 1950s. His riposte is instant. "You've got an enormous upheaval over the Suez crisis, the collapse of empires around the world, the Soviets going into Budapest ... There's not a decade without a crisis. A decade's an artificial construct: we're always characterising them because it's a journalistically attractive thing to do, but these are arbitrary time periods and very few historical phenomena keep like trains to those time frames."

Ferguson believes our economic crash is more akin to the one in the 1970s than the 1930s, and that proper remedial action has now been taken. The expenses furore is "a completely parochial British story, totally trivial, the opposite of world-historical". Historians pride themselves on seeing the truly significant trends that lie beneath our transient, often sensationalist, concerns, and Ferguson believes he can already see the one that counts. "The big turning point is nothing to do with radical Islam or, for that matter, the United States," he says. "The biggest turning point of our lifetimes is the transformation of China, which started in 1978. That's the game-changer."

The last word, though, must go to Eric Hobsbawm, here to mark the 90th anniversary of the Treaty of Versailles - an event that his birth predated by two years. Hobsbawm neatly manages to have it both ways. The noughties are a watershed because of the mid-decade economic meltdown, but it is too early to say how far-reaching the consequences will be. "Clearly the break in the world economy is the main thing that distinguishes this decade," he says. "It's the end, it seems to me, of a period of world history that began in the early 1970s. That period had begun with the failure to operate of the old Keynesian balanced economy of the postwar world, which had worked extremely well - better, actually, than anything since." He dismisses the war on terror as "a public-relations phrase invented by the Bushes". The instability in Pakistan could be a new source of danger, but again it is too early to say precisely how the story will develop.

So when will historians have a settled view of this decade? "I don't think historians will ever have a settled view," says Hobsbawm. "The view depends on where you stand. Just as I, looking back on the 1950s, have a different view now from what I would have had in the 1970s, so in the 2030s people will have a different view from what they will have in the 2040s. I don't think there is such a thing as a settled view." And don't look to Hobsbawm for predictions. "The only races we can predict," he says, "are the ones that have already been run." Even great historians - or perhaps only the greatest historians - know their limitations.